docs: def add_region_feature(self, start_resnum, end_resnum, feat_type=None, feat_id=None, qualifiers=None):
          """Add a feature to the features list describing a region of the protein sequence.
  
          Args:
              start_resnum (int): Start residue number of the protein sequence feature
              end_resnum (int): End residue number of the protein sequence feature
              feat_type (str, optional): Optional description of the feature type (ie. 'binding domain')
              feat_id (str, optional): Optional ID of the feature type (ie. 'TM1')
  
          """
          if self.feature_file:
              raise ValueError('Feature file associated with sequence, please remove file association to append '
                               'additional features.')
  
          if not feat_type:
              feat_type = 'Manually added protein sequence region feature'
          newfeat = SeqFeature(location=FeatureLocation(start_resnum-1, end_resnum),
                               type=feat_type,
                               id=feat_id,
                               qualifiers=qualifiers)
  
          self.features.append(newfeat)